This invention relates in general to disposal of drill cuttings generated from drilling a subsea well, and more particularly to a system that allows the cuttings to be injected into a drilled well.
When a subsea well is drilled, cuttings, which are small chips and pieces of various earth formations, will be circulated upward in the drilling mud to the drilling vessel. These cuttings are separated from the drilling mud and the drilling mud is pumped back into the well, maintaining continuous circulation while drilling. Ultimately, the cuttings must be disposed of.
In the past, these cuttings have been dumped directly into the sea. While such a practice is acceptable with water based drilling muds, oil based drilling cuttings would be contaminated with oil and would result in pollution if dumped into the sea. As a result, environmental regulations now prohibit dumping into the sea cuttings produced with oil based drilling mud.
There have been various proposals to dispose of oil based drilling cuttings. One proposal is to inject the cuttings back into the drilled well with a cuttings injection system. While systems exist in the prior art which allow injection of cuttings back into the drilled well, each has various drawbacks. The drawbacks include requiring detailed alignment of flow passageways, no provisions for twist that may occur while running the various casings, and requiring multiple runs to the well to set up the system. Therefore, there is a need for a simple cuttings injection system that can be run simultaneously with or after the wellhead housing and that compensates for twist in the wellhead requiring no detailed alignment of passageways.
The present invention is directed to an improved cuttings injection system for a well. The well has a wellhead housing and a casing hanger connected to a casing and sealed in the wellhead housing. The system has at least one flow port through a sidewall of the wellhead housing in communication with an annulus surrounding the casing. An injection ring on the wellhead housing has an external port and defines an internal annular gallery in communication with the flow port. A cuttings injector coupled to the injection ring that has a passageway sealable to the external port through which drill cuttings can be pumped for flowing through the gallery, flow port and into the annulus.
The lower end of the flow port is in communication with an inner surface of the housing below the packoff of the casing hanger and the upper end in communication with an outer surface of the housing above the packoff of the casing hanger. The at least one flow port comprises a plurality of flow ports. The injection ring is mounted to rotate relative to the wellhead housing. The well has guide posts and a first guide frame is joined to the injection ring adapted to engage the guide posts and position the injection ring. A second guide frame is joined to the cuttings injector adapted to engage the guide posts and position the passageway of the cuttings injector relative to the external port of the injection ring. The cuttings injector has an injection stab extendable into the external port to seal the passageway with the injection ring. The wellhead housing is supported by a low pressure wellhead housing and the injection ring is above the low pressure wellhead housing. The cuttings injector has a center ring that concentrically engages and supports the cuttings injector on the injection ring.